With rapid development of communications technologies, wireless communications technologies have been widely applied due to their advantages of convenience and efficiency in information transmission and low costs. However, as demands for spectrum resources in wireless communications systems continuously increase, spectrum resources for the wireless communications systems are decreasing gradually. As a type of non-renewable resource, a spectrum resource cannot be occupied simultaneously by another communications system once it is occupied by a communications system. To improve system bandwidth and solve a conflict between spectrum resources in communications systems and growing wireless communications demands, the 3rd Generation Partnership Project (The 3rd Generation Partnership Project, 3GPP) Long Term Evolution Advanced (Long Term Evolution Advanced, LTE-A) provides a technology of spectrum aggregation, that is, carrier aggregation (Carrier Aggregation, CA).
By using the carrier aggregation technology, multiple contiguous or non-contiguous component carriers (Component Carrier, CC) can be aggregated to obtain higher bandwidth, thereby increasing a peak data rate and a system throughput. In a communications system, after carrier aggregation is configured, user equipment (User Equipment, UE) may establish network communication by using multiple serving cells (Serving Cell) within a management area of one or more base stations (Base Station, BS). Frequencies of carrier components corresponding to different serving cells are usually different.
At present, in a process of configuring carrier aggregation, component carriers may be provided by a same base station, or may be provided by different base stations; the former is referred to as intra-base station carrier aggregation (Intra-BS CA), and the latter is referred to as inter-base station carrier aggregation (Inter-BS CA).
For the intra-base station carrier aggregation, in an LTE-A system, multiple co-site component carriers are provided by a base station, or multiple non-co-site component carriers are separately provided by a base station and a remote radio head (Remote Radio Head, RRH) of the base station. The base station configures, according to specific wireless conditions (such as channel quality, and pilot signal strength) and service conditions, carrier aggregation for UE that is located in a common coverage area of the foregoing multiple component carriers.
For the inter-base station carrier aggregation, UE may establish a radio connection relationship with one or more base stations that participate in carrier aggregation configuration, that is, establish network communication with multiple serving cells within a management area of the one or more base stations. In a process of configuring the inter-base station carrier aggregation, one base station (which is referred to as a first base station in the following) is responsible for data splitting/convergence usually. The first base station sends part of downlink data, such as a Packet Data Convergence Protocol (Packet Data Convergence Protocol, PDCP) protocol data unit (Protocol Data Unit, PDU) and a Radio Link Control (Radio Link Control, RLC) PDU, to one or more other base stations (which are referred to as second base stations in the following). As can be seen that, in the inter-base station carrier aggregation, the UE may receive downlink data by using radio links of multiple base stations, and send uplink data by using the radio links of the multiple base stations, and all the uplink data of the UE received by at least one of the foregoing second base stations is sent to the first base station that is responsible for data splitting/convergence. Referring to FIG. 1, FIG. 1 is a schematic diagram of inter-base station carrier aggregation in an LTE system. A first base station eNB1 and a second base station eNB2 separately schedule UE independently.
In a wireless communications system, after UE establishes a radio resource control (Radio Resource Control, RRC) connection with a base station, the base station schedules the UE. In the inter-base station carrier aggregation, multiple base stations that participate in carrier aggregation separately schedule UE independently. In a case in which a backhaul link (backhaul) is not in a desirable condition, referring to FIG. 1, the first base station eNB1 sends a first transport block TB1 to the UE, the second base station eNB2 sends a second transport block TB2 to the UE, and a total number of bits corresponding to the first transport block TB1 and the second transport block TB2 exceeds a bearer capability of the UE, causing that the UE fails to receive one of the transport blocks or fails to receive both transport blocks.
As can be seen that, during the inter-base station carrier aggregation, when multiple base stations send an excessively large amount of data to UE, the UE needs to discard some or all to-be-received data, causing a data receiving error.